1. Field of the Disclosure
This disclosure relates to electrochemical systems, e.g., a combination of an electrical energy source and an electrical energy storage system having a regenerative fuel cell system, that exhibit operational stability in harsh environments, e.g., both charging and discharging reactions in a regenerative fuel cell in the presence of an acid or a mixture of acids, or a halogen ion or a mixture of halogen ions. This disclosure also relates to methods of operating the electrochemical systems containing a regenerative fuel cell system. The electrochemical systems have low cost, fast response time, and acceptable life and performance.
2. Discussion of the Background Art
Fuel cells are electrochemical devices which can convert energy stored in fuels to electrical energy with high efficiencies. There are classes of fuel cells that also allow reversed operation, such that oxidized fuel can be reduced back to unoxidized fuel using electrical energy as an input. The ability to generate electricity and regenerate fuel makes these fuel cells suitable for electrical energy storage.
Acceptance of energy storage and generation technologies depends on their cycle life and performance capability. In particular, with regard to regenerative fuel cells, they can be run, in addition to the direct mode, in the reversible mode, consuming electricity and the products of the direct reaction in order to produce the reactants of the direct reaction. For regenerative fuel cell such as hydrogen/bromine fuel cells, an important factor limiting its cycle life and efficiency is the degradation of the operating fuel cell materials. These materials are exposed to a highly corrosive bromine electrolyte for long periods of time at elevated temperature.
Energy storage and generation devices are needed for wide application with regenerative energy sources. Such storage and generation devices are useful in matching a varying energy supply to a varying energy demand.
The world is facing a major energy and clean air challenges. Renewable energy systems using wind, sun, and water and utilizing advanced energy generating technology offer some potential solutions. Unfortunately, the current state of the art of conventional renewable energy sources, e.g., wind turbine generators and solar energy, and energy storage systems, and the integration of renewable energy sources and energy storage systems, have not been fully developed from a standpoint of efficiency and cost effectiveness to meet the challenges.
Current energy systems typically lack a commercially viable nighttime off-peak energy storage systems. Solid oxide fuel cell systems that generate electricity for utility use are generally designed to use natural gas or methane as the base fuel for hydrogen, thus contributing to air quality degradation. Integrated electrolysis systems have not been fully developed to use low priced off-peak produced renewable energy for producing hydrogen in a cost effective manner. There is a need to effectively integrate a combination of advanced renewable energy systems with energy storage systems to provide efficient and cost effective electrical energy for utility use.
A further need exists for energy storage and generation systems that exhibit operational stability in harsh environments, e.g., both charging and discharging reactions in a regenerative fuel cell in the presence of an acid or a mixture of acids, or a halogen ion or a mixture of halogen ions. Also, a need exists for energy storage and generation systems that are capable of conducting both hydrogen evolution reactions (HERs) and hydrogen oxidation reactions (HORs) in the same system. It would be desirable in the art to provide energy storage and generation systems having low cost, e.g., low cost reactant products, fast response time, and acceptable life and performance.
The present disclosure provides many advantages, which shall become apparent as described below.